Well you would need lots of experience working with flowers and I mean demonstrated experience. Start working in a flower shop and get to know all sorts of flowers and what they do there.
The key to becoming an arborist is to have a green thumb. There are degrees available as well as certificate programs at many local community colleges and universities.
Arborvitaes are evergreen trees, but becoming a florist provides you with a career where you can work with flowers. Visit your local flower shop for more information.